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Basin – A segment or portion of a larger watershed area, based on the natural water drainage pattern.

Biosolids – The organic by-product of wastewater treatment (also called “sludge”).Biosolids contain essential plant nutrient and organic matter and are recycled as a fertilizer and soil amendment.

Combined Sewer System – A one-pipe sewer system in which a single pipe collects both sewage and stormwater. In dry weather, all flow goes to a wastewater treatment plant. During wet weather, some flow may be diverted to CSO treatment facilities for storage and/or treatment. In heaviest rainfall, combined sewage flow may be discharged directly to streams

Consent Decree – A negotiated agreement by the City to implement a court-ordered directive to evaluate and implement short and long-term plans for eliminating water quality violations. The City is currently operating under three consent decrees, two of which resulted from lawsuits against the City, filed by the Upper Chattahoochee Riverkeeper, later joined by EPA and EPD. Two separate consent decrees address combined sewer overflows (CSO Consent Decree) and sanitary sewer overflows (First Amended (SSO) Consent Decree). A third consent decree addresses the City’s drinking water treatment and distribution system.

Consent Decree Remediation Deadlines – All construction associated with meeting the terms of the CSO Consent Decree and the First Amended Consent Decrees (FACD) must be completed by November 2007 and July 2014, respectively. Failure to meet these deadlines, and interim milestone deadlines in the FACD, will result in severe monetary penalties and a moratorium on development in the city.

CSO (Combined Sewer Overflow) – Designed discharge from a combined sewer system into a stream. Usually occurs during heavy rainfall.

EPA – U.S. Environmental Protection Agency: the federal agency responsible for enforcing the Clean Water Act, Safe Drinking Water Act and other federal environmental regulations.

EPD – Georgia Environmental Protection Division: the Georgia agency responsible for enforcing EPA regulations as well as state environmental standards.

First Amended Consent Decree – A second Consent Decree agreement, signed in 1999, that addresses Sanitary Sewer Overflows (SSOs) and operation of the City’s wastewater treatment plants.

Impervious Surface – A surface that does not allow water or other liquids to pass through it (for example, pavement).

NPDES – National Pollutant Discharge Elimination System; pollution control permits are issued under this system.

NPU – Neighborhood Planning Unit; the Neighborhood Planning Unit System was established to provide an opportunity for citizens to participate actively in the Comprehensive Development Plan: the City's vision for the next 5, 10, and 15 years. It is also used as a way for the citizens to receive information concerning all functions of City government. The system enables the citizens to express ideas and comment on City plans and proposals while assisting the City in developing plans which best meet the needs of different areas.

Raw Water – Intake water prior to treatment or use for drinking water.

Reservoir – Any natural or artificial holding area used to store, regulate, or control water prior to distribution into homes and businesses.

Safe Drinking Water Act (SDWA) – The main federal law that ensures the quality of Americans' drinking water. Under SDWA, EPA sets standards for drinking water quality and oversees the states, localities, and water suppliers who implement those standards.

Separated Sewer System – A two-pipe sewer system in which one pipe collects sewage and sends it to a wastewater treatment plant and the other pipe collects stormwater, which is typically discharged to a stream.

SSES – Sewer System Evaluation Survey (also Sanitary Sewer Evaluation Survey): A process of inspecting the inside of sewer pipes, using techniques such as Closed Circuit Television (CCTV), smoke testing, dye testing, flow monitoring and inspections to detect potential problems in sewer systems. The City’s SSES program, which began in June 2002, will address the entire system (2,200 miles) of pipe in the City.

SSO (Separate/Sanitary Sewer Overflow) – Sewage that flows out of a sanitary sewer pipe or overflow from a manhole onto the surface or into a stream. SSOs are a violation of the Clean Water Act.

Stormwater – Rainfall or other forms of precipitation. Stormwater runoff is the result of stormwater washing across impervious surfaces, carrying with it the pollutants found on streets, parking lots, rooftops, etc. These pollutants end up in streams and rivers. Stormwater runoff contributes from 60 to 80% of total water pollution.

Tunnelling – Use of an underground tunnel to convey wastewater, stormwater or combined flows to a treatment facility. Atlanta is already served by two wastewater tunnels - Three Rivers and Intrenchment Creek. A tunnel will be constructed in the Nancy Creek sewer basin to convey sanitary sewer flows from DeKalb to the R.M. Clayton WRC, providing relief from sewage overflows for northeast Atlanta residents. To address CSOs, tunnels will be constructed on the west and east sides of Atlanta.

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